Apparatus for coating the inside of pipe

ABSTRACT

A long and large pipe is placed on a traveling truck with rollers which cause the pipe to revolve on its axis. A cantilever boom is inserted into the pipe, while the rear end of the boom is attached to a support and a spray gun is located at the front end of the boom which is made to rotate against the revolving direction of the pipe. Feeding means for paint are inserted in the boom to the spray gun.

United States Patent [1 1 Takata et al.

[451 Jan. 7, 1975 1 APPARATUS FOR COATING THE INSIDE OF PIPE [75] Inventors: Tetsuo Takata; Yukio Nishino, both of Fukuyama, Japan [731 Assignees: Nippon Kokan Kabushiki Kaisha,

Tokyo; Ohmiya Kigyo Kabushiki Kaisha, Osaka, both of, Japan [22] Filed: Sept. 25, 1972 211 Appl. No.: 291,564

[30] Foreign Application Priority Data Sept. 28, 1971 Japan 46-75031 [52] US. Cl 118/318, 118/321, l18/DIG. 1O [51] Int. Cl. B05c 7/02 [58] Field of Search 118/318,D1G. 10,317,

[56] References Cited UNITED STATES PATENTS 221,939 Root ll8/D1G. l0

2,303,088 11/1942 Perkins l13/DIG. 10

2,373,638 4/1945 Perkins l18/D1G. 10

2,602,415 7/1952 Hall ll8/D1G. 10

3,230,105 l/1966 Spraul et a1 118/318 X 3,351,289 ll/l967 Demaison 118/323 X FOREIGN PATENTS OR APPLICATIONS 496,499 l2/l938 Great Britain 118/318 Primary Examiner-John P. Mclntosh Attorney, Agent, or FirmGeorge B. Oujevolk [57] ABSTRACT A long and large pipe is placed on a traveling truck with rollers which cause the pipe to revolve on its axis.

A cantilever boom is inserted into the pipe, while the rear end of the boom is attached to a support and a spray gun is located at the front end of the boom which is made to rotate against the revolving direction of the pipe. Feeding means for paint are inserted in the boom to the spray gun.

1 Claim, 3 Drawing Figures Pintcnted Jan. 7, 1975 2 Sheets-Sheet 1 WLF 1 APPARATUS FOR COATING THE INSIDE OF PIPE BACKGROUND OF THE INVENTION The present invention relates to a coating apparatus for the inside of a long and large pipe, and more particularly to forming a uniform and thick coating film on the inside of a pipe.

BRIEF DESCRIPTION OF THE PRIOR ART In coating the inside of a pipe, it is difficult for a uniform film to be'formed. It is well known that various difficulties occur when the diameter of the pipe is more than 500 mm and the length of the pipe is more than meters. For this type of pipe, various coating processes and pieces of apparatus have been proposed and put into practice as for example, theCRC Cross type or the Midwestern type are well-known typical examples.

The CRC Cross type is characterized by a boom mechanism, that is, it comprises a boom of about 13 meters in length, with a spray gun fixed to one end of the boom, a support is arranged near this end and a traveling truck is provided. In operating this mechanism, first, a pipe is clamped and caused to rotate with multi-pairs of turning rollers. Then the boom is inserted into the pipe by the traveling truck. After this, the coating is done by a fixed spray gun during the rotation of the pipe. In this system, the pipe will be coated only on the return stroke of the boom because the film may be injured by the supporting device if the coating operation is performed during the delivery stroke of the boom. Needless to say, the above described operation results in several defects. A film of heavy thickness of about 100 microns is difficult to form because a reciprocating operation of the spray gun isnecessary to form a heavy thick film. However a reciprocating operation cannot be performed as just explained. Furthermore, a uniform film is difficult to fonn because the spray gun is fixed to the front end of the boom and the pipe itself rotates. According to many experiments, it has been confirmed that a high peripheral velocity of pipe rotation such as 180 m/minute is necessary to form a uniform film. It will follow that such rotation at a'hi'gh peripheral velocity brings about vibrations of the pipe body by a curve in said body, weld bead or the like. such vibrations of the pipe body exert a serious influence upon the traveling of the long boom and the supporting devices of the boom, consequently it becomes difficult to form a uniform film. Thus, the aforementioned CRC Cross type mechanism requires considerable improvement.

The Midwestern type is characterized by a truck mechanism traveling on the inside of the pipe, that is, a rotating device with a spray gun, high pressure hose and electrical cables, etc. are arranged on the truck. Such a mechanism tends to bring about irregularity in the traveling speed of the truck in connection with curves, weld bead, etc. of the pipe. It will follow therefore that the film is not uniform, that is, the film is thin as the travel speed becomes rapid and thick as the speed slows down. Also, a heavy thick film is difficult to form for reasons similar to that of the CRC Cross type as hereinbefore mentioned. furthermore, the formed film tends to thin on the upper wall and thicker on the lower wall of the pipe because of the action of gravity since the pipe body is standing still. In the foregoing mechanism, an off-flow valve for spraying is placed on the pump feeding the paint. Accordingly, it is unavoidable that the paint in the pipe dripsand falls in drops from the spray gun when stopping the flow of paint. Therefore, a receiving vessel for the dripping'of the paint has to be arranged on the spray gun in the delivery stage of the spray gun of the truck, and is removed during the return stage of the truck. These are troublesome operations, and the Midwestern type arrangement also needs to be improved.

SUMMARY OF THE INVENTION This invention has been developed in the light of the foregoing difficulties and defects. Generally speaking, the present invention contemplates the combination of a travelling truck on which a pipe is placed and a boom wherein the rear end is supported by the housing, while a spray gun is fitted to the front end of the boom. In this combination, the pipe and spray gun are caused to rotate in opposite directions to each other.

OBJECTS OF THE INVENTION Thus, an object of this invention is to provide an apparatus for coating the inside of a pipe capable of coat ing a uniform film on said inside.

Another object of this invention is to provide an apparatus for coating the inside of pipe capable of freely controlling the thickness of the film.

Other objects and advantages will be apparent from the following description and accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective and side elevation of the inventive concept;

FIG. 2 is a perspective and cut-out side elevation of the coating apparatus shown in FIG. 1;

FIG. 3 is a partial plane view of the components shown in FIG. 1.

- DETAILED DESCRIPTION Referring now to FIG. 1 and FIG. 3, a truck 6 travels on guide rails 11 by a drive motor 13. The pipe 12 to be coated is placed on said truck 6 by means hereinafter described. Accordingly, the length of the truck 6 depends on that of the pipe 12.

Pipe 12 is moved on skid rails (not shown) and then held by a pair of stoppers 7 through kick-out rail 8 connecting to said skid rail. At this point, pipe 12 is positioned on turning rollers 9. A number of units comprising the kick-out rail 8, a pair of stoppers 7 andv turning rollers 9 are arranged in accordance with the length of truck 6. In these drawings, three units are shown. The turning rollers 9 of each unit revolve by a drive motor 14 in a body. Needless to say, the rotation of rollers 9 is freely controlled in accordance with the diameter of said pipe 12.

The positioning of pipe 12 on truck 6 is operated from a coating booth 10. After that, the truck 6 returns to the coating booth l0 and the front end of pipe 12 is positioned for a spray gun 2 arranged hereinafter described.

As shown in FIG. 2, the'spray device 2 comprises a head which is fixed to a rotatable shaft 16, and guns which are arranged on the head. And then, a feed hose for paint and another hose for compressed air are inserted into said shaft 16 and connected to spray device 2. The rotatable shaft 16 is supported with a boom 1, that is, the shaft 16 is inserted into boom 1 and coupled to boom 1 with known rotatable means. Shaft 16' is turned by a drive motor 4. Also used is a joint 3 of the rotary type and connects each of the hoses to the corre- I sponding pipe 19. Both liquid and powder paint can be used.

The boom 1 playing a supporting part for rotatable shaft 16 is of cantilever type, that is, the rear end is held with a housing 5 and accompanied with a balance weight 7 as shown in FIGS. 1 and 3. Such a balance weight 17 is effective'in reducing the load of the front end of the boom 1 and making the coating operations stable. Boom lcan be moved up and down by a drive motor 15. With this arrangement boom 1 is easily held at a predetermined position when there is a change of the pipe diameter to be coated.

The coating starts at a position at a front end of pipe 1 corresponding to spray gun 2. It is an important factor that the revolving of the pipe 12 and the rotating of spray gun 2 are carried out in the opposite direction. Because, when pipe 12 and spray gun 2 are rotated in the opposite direction of each other, the revolving of the pipe 1 does not need to be operated with such high peripheral velocity as hereinbefore mentioned in relation to prior art arrangements. For example, the best coating possible is easily obtained by controlling rotation of the spray gun even if the revolving of the pipe is at a low speed. Such a correlation produces great advantages, that is, no vibration of pipe body as hereinbefore mentioned, as takes place in the prior art systems and the non-uniformity of the film because of the vibration, etc. Another important advantage lies in the cantilever arrangement of the boom, that is, the supporting of only the rear end. By such a mechanism, the reciprocating motion of the truck is possible and easily and freely obtained without injuring the film on the inside of the pipe. Accordingly, the thickness of the film can be easily and freely controlled as well as the uniformity of said film.

Thus, when the rear end of pipe 12 comes outof coating booth 10, the coating operation is completed,

that is, the travelling truck is stopped, at the same time a stop valve (not shown) arranged in spray means 2 acts. In such a case, there is no dribble, the pipe 12 is removed from truck 6 by kick-out rail 8.

According to this invention, the controlling of the thickness and the keeping of uniformity of the inside film is readily possible.

We claim:

1. Apparatus for coating the interior surface of an elongated pipe comprising guide rails, a pipe carrying truck mounted on said rails for reciprocating movement thereon, pipe supporting rollers on said truck for a rotatable supporting of a pipe, means on said truck rotating a supported pipe in a predetermined direction, a cantilevered boom aligned with said rails for selective coaxial introduction and movement of the outer end thereof into and along the entire length of a truck mounted pipe upon a reciprocating movement of the pipe truck on the rails, support means aligned with said rails and beyond the limit of movement of the truck, said boom,-toward one end thereof, being mounted on said support means with the boom projecting therefrom and overlying the rails for the aforementioned introduction of the outer end thereof into a truck supported pipe, and a shaft extending longitudinally through said boom and beyond the outer end thereof, said shaft being rotatably mounted within said boom, means rotating said shaft in a direction of rotation opposite from that of the pipe to be coated, and a spray head including angularly spaced radially directed spray guns mounted on the outer end of the rotatable shaft beyond the outer end of the boom. 

1. Apparatus for coating the interior surface of an elongated pipe comprising guide rails, a pipe carrying truck mounted on said rails for reciprocating movement thereon, pipe supporting rollers on said truck for a rotatable supporting of a pipe, means on said truck rotating a supported pipe in a predetermined direction, a cantilevered boom aligned with said rails for selective coaxial introduction and movement of the outer end thereof into and along the entire length of a truck mounted pipe upon a reciprocating movement of the pipe truck on the rails, support means aligned with said rails and beyond the limit of movement of the truck, said boom, toward one end thereof, being mounted on said support means with the boom projecting therefrom and overlying the rails for the aforementioned introduction of the outer end thereof into a truck supported pipe, and a shaft extending longitudinally through said boom and beyond the outer end thereof, said shaft being rotatably mounted within said boom, means rotating said shaft in a direction of rotation opposite from that of the pipe to be coated, and a spray head including angularly spaced radially directed spray guns mounted on the outer end of the rotatable shaft beyond the outer end of the boom. 